1. Field of the Invention
The present invention relates to a laser treatment apparatus that irradiates a surface of a substrate with a laser beam, while a substrate holding unit moves horizontally and the surface of the substrate is supplied with a liquid, thereby to perform a laser treatment to the surface.
2. Description of the Related Art
As one of series of processes for fabricating a semiconductor device, a process is known, which process machines a substrate, such as a semiconductor wafer and a glass substrate for a liquid crystal display, by using a laser beam.
US patent application publication No. 20020050489 A1 (Ikagami et al.) discloses a technique that scans a substrate surface by a laser beam to form dicing lines thereon. US patent application publication No. 20040197433 A1 (Terada et al.) assigned to the same assignee of the present application discloses a technique that removes a resist film on an alignment mark formed on a substrate by using a laser beam in order to expose the alignment mark before exposure of the substrate. The use of a laser beam is effective for such treatments, because it has a high energy and can be positioned precisely.
When machining a substrate surface by using a laser beam, a substrate surface is irradiated with a laser beam while a liquid such as deionized water flows on the substrate surface, in order to prevent re-adhesion of substances removed by the machining to the substrate surface.
FIG. 11 schematically shows the structure of the laser machining apparatus of US 20040197433 A1. A chuck 13, which is capable of rotating by means of a drive mechanism 12, is arranged in a cup 11. A substrate 10 held by the chuck 13 is irradiated with a laser beam by means of a laser beam irradiating unit 14 while the chuck is moved in X- or Y-directions by means of a moving mechanism, thereby a resist film overlying an alignment mark is removed.
When irradiating a laser beam, a plate 15 made of a transparent quarts glass is placed such that it is slightly removed away from a surface of the substrate 10, and deionized water is supplied into a gap between the plate 15 and the substrate 10 from one side while the deionized water is sucked from the other side to be collected. After completion of the treatment by the laser beam, the plate 15 is raised, and a spin-drying, which removes the deionized water on the substrate 10 by rotating it, is performed.
During the irradiation of the laser beam, an amount of deionized water which can not be sucked is spilled from the wafer to fall into the cup 11. If the irradiated position is near the periphery of the substrate 10, a large amount of deionized water falls into the cup 11. When spin-dying the substrate 10, deionized water also scattered into the cup 11. Thus, the cup 11 must be provided in its bottom with a drain port to discharge the deionized water from the cup 11. Moreover, in order to prevent water droplets scattered during the spin-drying of the substrate 10 from going out of the cup 11, the cup 11 must be provided in its bottom with an exhaust port to form an air flow that draws the water droplets into the bottom of the cup 11. In the laser machining apparatus of US 20040197433 A1 is provided with an exhaust port 16 which is commonly used as the aforementioned drain port and exhaust port.
As the cup 11 moves X- and Y-directions by means of the moving mechanism, a flexible hose (exhaust pipe) long enough to adapt the moving range of the cup 11 must be connected to the cup 11. As the cost of a clean room per unit area is very high, semiconductor fabricating apparatuses are downsized, and component parts of the apparatuses including driving mechanisms are arranged in bottom spaces of the apparatuses in a high density. Thus, making a sufficiently wide space for the hose is difficult, in other words, prevents downsizing of the apparatus.
In addition, as a semiconductor fabricating apparatus has a number of driving mechanisms, it is preferable to use a possible smallest drive source for each driving mechanism. However, the curved flexible hose connected to the cup 11 offers a great resistance to the movement of a stage to which the cup 11 is mounted. In order to move the stage at a high speed and a high acceleration to ensure a high throughput of the apparatus, a high-power, thus large-sized drive source must be used. This problem becomes more noticeable in recent days when the size of a substrate (in a case of a semiconductor wafer, 12-inch size) becomes larger.